Challenges are encountered when plastic meltblown fibers are melt extruded from a synthetic resin to form a meltblown nonwoven fabric. Ordinarily a large number of threads are extruded from a single extrusion head, and among the challenges that are encountered are obtaining uniform thread size, uniform temperature across the whole of the extrusion head, and uniform flow distribution and pressure on extrusion orifices or spinnerettes. It would be desirable to provide an apparatus and a method of extruding a large number of fibers that provides uniform flow and temperature to the polymer composition from which the fibers are extruded and that imparts the same processing conditions and processing history to the melted polymer compositions at similar positions in the melt extrusion process. The spinnerettes may be single orifice spinnerettes for monofilament threads or groups of orifices to produce a multi-filament thread. Spinnerettes are well known and are described and illustrated in U.S. Pat. No. 4,445,833 the disclosure of which is hereby incorporated by reference herein.
An early attempt to extrude improved melt extruded fibers and nonwoven materials was suggested in U.S. Pat. No. 3,825,380 to Harding et al. However, U.S. Pat. No. 3,825,380 does not disclose or teach an apparatus for extruding multicomponent fibers and nonwoven materials, particularly sheath/core meltblown fibers and other complex meltblown fiber structures. Other attempts to solve the problems are presented in U.S. Pat. No. 4,828,464 to Lau et al., U.S. Pat. No. 6,461,133 to Lake et al. and U.S. Pat. No. 6,474,967 to Haynes et al.
Sheath/core like meltblown fibers can be produced by using an ABA structure and matching the viscosities of the sheath forming polymer resin and the core forming polymer resin to cat-eye fibers as described in U.S. Pat. No. 6,747,967 to Haynes et al. It would be desirable to provide a die tip, an apparatus, and/or a process that can be used to produce true bicomponent meltblown sheath/core fibers and other complex meltblown fiber structures that is less dependent on viscosity matching of the components.